In-Vivo Frame Dynamicity of Self-Expanding Transcatheter Aortic Valves.
BACKGROUND Due to nitinol stent properties, self-expanding transcatheter heart valves (THVs) have the potential to adapt their frames to native annular dimension excursions during the cardiac cycle and therefore to maintain the physiological relevance of this behaviour. AIMS To assess the in-vivo variations of THV frame dimensions during the cardiac cycle. METHODS Patients undergoing transcatheter aortic valve replacement (TAVR) with self-expanding THV platforms enrolled in the RE-ACCESS 2 study were considered. Patients with post-TAVR four-dimensional computed tomography (4-D CT) assessment not eligible for stent frame analysis were excluded from the analysis. The THV frame dimensions were assessed at three levels: inflow edge, native virtual basal ring (VBR) and bioprosthetic leaflets plane (BLP). Measurements were performed in systolic (30° of the cardiac cycle) and diastolic (70° of the cardiac cycle) phase acquisitions for each patient. Stent expansion was reported as the difference among systolic and diastolic measurements. RESULTS Among a total of 127 patients, 83 patients were considered eligible for the present analysis. Forty-nine and 34 patients received Evolut and Acurate Neo2 THV, respectively. Stent frame expansion across the cardiac cycle was encountered at VBR (median perimeter variability 0.30 mm) and BLP (median perimeter variability 0.25 mm) levels, but not at the inflow level (median perimeter variability -0.05 mm). Acurate Neo2 had greater variability compared to Evolut THVs (VBR median perimeter variability 0.50 mm vs. 0.10 mm, p = 0.02; BLP median perimeter variability 0.60 mm vs. 0.20 mm, p = 0.05). CONCLUSIONS Self-expanding THVs exhibited dynamic behavior throughout the cardiac cycle, with stent expansion during systole at both VBR and BLP levels. Stent design influenced this dynamicity, as Acurate Neo2 had greater stent variability compared to Evolut THV. Whether these features affect long-term THV durability remains to be determined.